How to understand your SIP error codes

Getting Started

Some SIP phones and all PBX's will display an error or a prompt using the SIP Response codes, this document contains a list of SIP codes which can help you diagnose problems.

SIP response codes, class 1: Provisional messages These are sent within a SIP dialogue

• 100 Trying
• 180 Ringing
• 181 Call Is Being Forwarded
• 182 Queued
• 183 Session Progress

SIP Response codes: 2xx class The 2xx class of responses indicates a success

• 200 OK
• 202 accepted: Used for referrals

SIP response codes, class 3xx The 3xx class of responses indicates a redirection of the call

• 300 Multiple Choices
• 301 Moved Permanently
• 302 Moved Temporarily
• 305 Use Proxy
• 380 Alternative Service

SIP responses, class 4: Request failures

• 400 Bad Request
• 401 Unauthorized: Used only by registrars. Proxys should use proxy authorization 407
• 402 Payment Required (Reserved for future use)
• 403 Forbidden
• 404 Not Found: User not found
• 405 Method Not Allowed
• 406 Not Acceptable
• 407 Proxy Authentication Required
• 408 Request Timeout: Couldn't find the user in time
• 409 Conflict
• 410 Gone: The user existed once, but is not available here any more.
• 413 Request Entity Too Large
• 414 Request-URI Too Long
• 415 Unsupported Media Type
• 416 Unsupported URI Scheme
• 420 Bad Extension: Bad SIP Protocol Extension used, not understood by the server
• 421 Extension Required
• 422 Session Interval Too Small
• 423 Interval Too Brief
• 480 Temporarily Unavailable
• 481 Call/Transaction Does Not Exist
• 482 Loop Detected
• 483 Too Many Hops
• 484 Address Incomplete
• 485 Ambiguous
• 486 Busy Here
• 487 Request Terminated
• 488 Not Acceptable Here
• 491 Request Pending
• 493 Undecipherable: Could not decrypt S/MIME body part

SIP responses, class 5: Server failures

• 500 Server Internal Error
• 501 Not Implemented: The SIP request method is not implemented here
• 502 Bad Gateway
• 503 Service Unavailable
• 504 Server Time-out
• 505 Version Not Supported: The server does not support this version of the SIP protocol
• 513 Message Too Large

SIP response codes, class 6: Global failures

• 600 Busy Everywhere
• 603 Decline
• 604 Does Not Exist Anywhere
• 606 Not Acceptable